"DC Haumaha showed a lack of judgement in expecting an autocratic management style to get the best from an inter-agency team."

National leader Simon Bridges has called it a "damning report" and says Ms Ardern needs to take responsibility.

"It was Prime Minister Jacinda Ardern who appointed Wally Haumaha. She now has to take responsibility and dismiss the man that she appointed to one of the most senior and powerful roles in the country," he says.

"It would be unconscionable for Mr Haumaha to stay in this constitutionally important role given the seriousness of the IPCA findings."